1. Field
The present disclosure relates generally to metrology of forests and, in particular, to making measurements of a forest below the canopy of a forest. Still more particularly, the present disclosure relates to a method and apparatus for making measurements of trees using a sensor system.
2. Background
Forestry management is a branch of forestry that includes many different aspects. These aspects may include environmental, economic, administrative, legal, and social aspects of managing a forest. Forestry management may consist of various techniques such as timber extraction, planting trees, replanting trees, cutting roads and pathways through forests, preventing fires in a forest, maintaining the health of the forest, and other suitable activities.
When performing these and other operations with respect to forest management, a forest inventory may be performed to collect information about the forest that may be desired. A forest inventory is an identification of information about a forest for assessment or analysis.
For example, a forest inventory for the forest provides an ability to analyze the state of the forest as well as identify operations that may be performed. This information may be used to identify things such as types of trees, height of trees, age of trees, value of trees, and other suitable information about trees in the forest. For example, a number of trees per acre may be identified through forest inventory. Additionally, forest inventory also may be used to identify other information such as vegetation, wildlife, or both within a forest.
These operations that may be performed using a forest inventory may include, for example, at least one of replanting trees, harvesting trees, performing timber stand improvement activities such as pruning and treating trees, performing pest removal, generating warnings of potential fire conditions, and other suitable operations. As used herein, the phrase “at least one of”, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of each item in the list may be needed. For example, “at least one of item A, item B, and item C” may include, without limitation, item A or item A and item B. This example also may include item A, item B, and item C or item B and item C. In other examples, “at least one of” may be, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; and other suitable combinations.
One manner in which information may be obtained about a forest as part of a forest inventory is performing aerial surveys. Although the use of manned or unmanned aerial vehicles may provide information about the forest, this type of measurement of the forest may not provide as much information as desired. Aerial surveys are typically unable to generate information about the portion of the forest that is below the canopy. The canopy of the forest is the uppermost foliage in the forest. The canopy may be formed by the crowns of trees in the forest. Information such as tree height and tree counts may be made using aerial surveys. Other information, however, such as information about a tree diameter, tree taper, tree defects, and tree damage may not be measured as easily using aerial surveys.
Currently, personnel are sent into a forest to make measurements of the diameters of a tree as well as other measurements with respect to the portion of the trees below the canopy. Collecting information about all of the trees in the forest using personnel may be extremely expensive and prohibitive with respect to time and difficulty reaching trees on different types of terrain. As a result, measurements are made only for some of the trees to generate a sampling of trees in the forest. The diameters of other trees may be estimated by extrapolating from ground samples, or by using an empirical regression model with respect to age and tree height as measured from aerial surveys.
Sending personnel into the field to measure diameters of trees may be time consuming and costly. Estimating a tree diameter using tree height information may lead to inaccuracies. These inaccuracies may not provide a desired level of information to evaluate the quality in value of trees in a forest for harvesting purposes or maintenance purposes.
In some illustrative examples, a higher sampling of trees may be performed using a terrestrial survey performed from the ground using a terrestrial light detection and ranging system operated by a human operator. These types of systems are line of sight systems requiring a line of sight from the light detection and ranging system to the tree being measured. As a result, personnel are still required to enter the field and walk through a forest to make measurements. This type of measurement still requires considerable time and may be more expensive than desired to obtain a desired quality of information about the trees.
Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as ether possible issues.